i tried doing this once. but it depends which style game ur looking for.
Super Mario World (the one with the cape) has Lunar Magic. REALLY good.
Super Mario 3 has this weird program I have. It's very useful, but it's unstable though, and has some weird problems with events.
If you want to make it yourself, I believe there is Game Maker starter kit I downloaded called "2D platformer maker."
If you want any of these, and can't find it, PM me.